Centrifugal pump with self-priming characteristics



July 18, 1961 H. H. KROEGER CENTRIFUGAL PUMP WITH SELF-PRIMING CHARACTERISTICS Filed Oct. 23, 1958 2 Sheets-Sheet 1 FIG. 2

HENRY HKROEGER INVENTOR. BYAQ uu- M July 18, 1961 H. H. KROEGER 2,992,617 CENTRIFUGAL PUMP WITH SELF-PRIMING CHARACTERISTICS Filed Oct. 23, 1958 2 Sheets-Sheet .2

FIG.7

HENRYHKROEGER INVENTOR.

BY W

U d State .f ae tQ 2,992,617 OENTRIFUGAL PUMP WITH SELF-PRIMING CHARACTERISTICS Henry H. Kroeger, Montclair, N.J.,; assignor -to Worthington Corporation, Harrison, NJ., a corporation o f Delaware Filed Oct. 23, 1958, Ser. No. 769,201 3 Claims. (Cl. 1035-103) This invention relates generally to' the pumping of fluids and more particularly to an improved centrifugal pump design for pumping a heterogeneous mixture of liquids, gases and solids.

It is well known that the pumping of heterogeneous mixtures of liquids, gases and/ or solids presents a difiicult pumping problem for a centrifugal pump because such mixtures adversely affect the performance characteristics of the pumps and cause unstable operation where the pumps are not designed to handle this type of fluid ture. This is particularly so when the pump is designed primarily for handling homogeneous fluid. a

When a pump designed for handling a substantially homogeneous fluid is required to-pump a, heterogenous mixture of liquids, gases and solids it is believed that secondary movement of thefluid" being pumped is profgressively reduced to. a minimum. and finallythe pump is rendered inoperative by gas binding. p H

It is believed that this occurs due to the counter-effect between the centripetal field and the discharge capacity andflpressure head. When a heterogeneous mixture of liquids, gases and solids is fed to the rotating impeller of a pump normally designed to handle a substantially homogeneous fluid the centripetal field produced by the rotating impeller will first act like a centrifuge separating and. stratifying the various components of the mixture in accordance with their densities and, secondly, will induce a secondary of counterflow of the less dense components, i.e., the gases and like density materials flow towards the suction inlet or area of lower pressure in the passages formed in or relative to the impeller. This Stratification and counterflow reduces the thruflow discharge capacity and pressure head of the pump. Asthe discharge capacity and. pressure head is reduced there results a corresponding increase in the centripetal field which in turn increases separation, stratification and counterflows Now a further reduction in' the discharge capacity'and pressure head occurs and the process repeats itself until a heavy layerlofzstratified material is formed about a core "of separated gasesin the center of the centripetal field which core will continue to build up until thevarious forces 2,992,617 Pa en J 8 we gases and solids being pumped whereby a pump for this type mixture with good performance characteristic j is provided. .I-

f U It is anotherobject of'the present invention to provide a centrifugal pump having an optimum design configuration including a regenerative acting impeller tip of a predetermined configuration and apparent to oneskilled in the art which will impart a spiral or helical mot-ion to the forward motion of a heterogeneous mixture of liquids, gases and solids being pumped, and which is further adapted in the portion of the vane channels for. the impeller adjacent the periphery of the impeller and in the volute to accelerate the centrifugal component of the helical mot-ion to a maximum when the thru flow decreases to zero thus providing self-priming characteristics in addition to high performance and stable operation in this type of pump when heterogeneous fluid mixtures or mixtures having high gas content or which froth or evapcrate easily are handled. 1. Itis another object of the present invention to provide a centrifugal pump having an optimum design configuration for imparting a spiral or helical motion to the forward motion of a heterogeneous mixture of liquids, gases "and solids being pumped so that a hydrodynamic back- -flow cut-off is provided forthe less dense part of the fluid either at the entrance of the impeller or in the point of flow between the discharge-of'the vane channels in the impeller and the voluteythe backflow cut-olf e'ifect increases as capacity decreases and is at a maximum whencapacity drops to zero thus providing good selfprimingfeatures for this design.

Further objects and advantages of the inventionwiH become eviden t-from the following description with reference to' the accompanying drawings in which:

FIGURE 1 is a side view of a centrifugal pump partly in vertical section showing the invention therein. j j

FIGURE 2 is a vertical section taken on line of FIGURE 1.

FIGURE 3 is a section taken on line -3--3 of FIGURE 2 with the impeller removed. I

FIGURE 4 shows another form of centrifugal pump, partly in vertical section, showing a modifiedforiii of the invention. 7 a

FIGURE 5 is a side view of a centrifugalpump partly in vertical; section, showing another form of the invention. FIGURE 6 is a side view of a centrifugal pump partly in vertical section, showing still another form of the pres and pressures acting in the impeller and the flow passages H are equal, at which point eifective pumping ceases. 'Ihe present invention seeks to overcome the problem by providing a centrifugal pump wherein a" helical motion is imparted to the fluid asit enters the vane of the impellerwith the provision of a tongue in the pressure developing passage means formed in the impeller which flowfluid from the suction inlet to the discharge outlet. This helical motion is amplified at the outer periphery of the impeller and in the volute and discharge chamber with the provision of regenerative tips on the outer edge of the pressure developing passage means and formation of the volute to return fluid to these tips with the least amount of shock. The helical motion resulting coacts witha curvilinear flow pattern provided by a suction tube formed at the pump inlet to aforementioned difficulties. 5 j Accordingly, it is an object of the present invention to provide ancentrifugal pump having an optimum design configuration for imparting a spiral or helical motionrto the forward motion of a heterogeneous ,mixture of liquids,

cut invention. t i

FIGURE 7 is a fragmentary view of the press ure developing passage means of the impeller showing the tongue means for creating the helical motion. f

FIGURE 8 is a fragmentary vied/0f anflbpen imp elle r showing the tongue means for creating the helicaljnotior i. FIGURE 9 is a'perspective view on line 9'9 of FIG- URE 8 showing the tongue contemplated by this insubstantially reduce the vention.

Referring to the drawings; FIGURE 1shows"'a:centrifugal pump including a casing generally designed-=1 having a suction inlet 2, a discharge outlet 3, and a volute 4 which communicates with the discharge outlet asshowil in FIGUREZ of the drawings.

Ashaft 5 extends through the side of the casingremote from the suction inlet side 'intoan impeller chamber as at 6 which shaftis rotated by any suitabletyp of prime mover, not shown, as lis'well knownin the Disposed in the impeller chamber 6 is an impeller 7- which-is" fix edly mounted onthe end of theshaft 6 as=by a threaded element8.1 w 3 In the present invention there are a number ofdistmct configurations :which coact to impart thedesired'helical motion .1120. theJforIward motion of the fluid hej'rigipumpe'd,

These may beenumeratedasz" (a) the tongue 50 formed iatfi'e'pre'ssnre uveieping passage means 51"forme'dbetween opposite vanes of theiimpeller 7; (b) the regenera- ,ti ips l'] of predeterminedconfiguration formed on the i d ed'ge er fthe' pressure developing passage means 51; iid' (c)"the configuration o'f'the volute '4forpass'ing fluid discharged from the impeller back into the tips" 16 in 'ash'oekless fashion; V V

. Curvilinearflow path Afiixed to'the portion of the 'su'c ti'oninlet adjacent the impeller chamber fi is "an annular ring-like element 10 referred Zto' as'a suction tube. The inner face of this 'eler'neht provides a smooth continuation of' the suction inlet up'to the suctioney'e'9 of"the=impeller, which face as at 11 reducesfrom the diameter of the'suction inlet to the diameter of'the"su'ctioneye of the impeller to provide flan" area of variable cross-section as is clearly *shown'in FIGURE '1' of the drawings.

"Whenfluidtravels'fro mthe suction inlet through this -annu'lar'ring'to the suction eye of the impeller a pre-entrance flow path having 'curvilinear'motion without rotation is developed. This curvilinear motionin'such channel-of variable cross-section will counteract'separation -and movementof lighter components of'the heterogeneous -mixture of fluids; gases and solids being pumped towards thelow 'press'ure areas of the impeller.

,Thisis believed to occur in curvilinear motion because 'initial forces acti'ngin'the fluid and centrifugal forces developed: in turning the fluid tend to produce secondary cross-flows which move or carry the lighter components ;of' the'rnixtures away from the walls in a'direction normal to the bending of the flowlines projduced by the shape of the passage'carrying the fluid mixture. This result is advantageously applied to the present invention to prevent accumulation of gases at spots critical to the operation and performance characteristics of this pump. N

In additionmanipulation of the flow in a curvilinear fashion as is provided for by suction tube 10 also provides a block for the lighter fluids caught in the eye of the 'helixpreated by the means mentioned hereinabove to arrest it from passing back into the low pressure areas of the suction eye 9.

Tongue "means "As the flow enters the pressure developing passage means 51 of the impeller 7 a helical motion is. imparted thereto bythe provision of tongue means'50 which comprises an extension of the vane forming a side'of the passage means 51. The tongue formed of a predetermined .configurationto thereby create a low pressure area therebehind at 52 and accordingly induce a helical motion to .the fluidpassing through the passage means 51. I V

While EIGURES I and 7 show the tongue 50 formed on an impeller of the closed type it;is not intended to limit the construction to this configuration as the tongue maybe applied to an impeller of the open type as is shown in FIGURE 8 of-the drawings.

- In order to impart the helical motion to the forward ,motion' of the'fluid being pumpedthrough the portion 'of tthe vanes adjacentthe periphery of the impeller and in the .volute in the casing, the peripheral portion of the impeller is shaped as shown in FIGURE 1.

'Thus FIGURES 1 and 2 show that the impeller includes aback shroud lz continuous with the hub 13; a front shroud14 of a lesser diameter than the back shroud, and a; pluralityof circumferentially disposed radially extending curved vanes 15. a v a The fyanes have their-iinner or entering end disposed just inwardly of the suction eye 9 and extend in a'curved rearward-1y --bending path-beyond thefperiphery of the shorter front shroud 14101116 periphery of'the r'ear sh'rond 19i The ti'p -16"of each of the 1 vanesis" shown in EIG= URES 1 and 2 as having a cutback as at 17 formed of a "predetermined configuration and one that will providethe Configuration of the volute Thefvolute 4 can take'a number of configurations" which 'adapt' it to-coact with the regenerative tip for the "impeller 7. The preferred form for the volute being a' construction that 'will provide for return flow to the regenerative tips in a substantially shockless fashion and by way of example FIGURE 1 indicates a means of adapting a conventionalvolute to the present invention.

In FIGURE 1 thenormal curvature of the volute lis cut back on its forward or front face'as at 18 to'prbvide a smooth continuous chamber substantially'cifrculafin crosssection which is continuous from the periphery of the rear shroud to the periphery of the front shroud. y

Thus a portion of the volute 4 extends below the outermost point 'of-the vane tip 16 and will coact with'the' cutbaekpo'rtions 17 of each of the vanes 15"to"all6w the fluid being rotated by the impeller andpumpe'jd'iritofthe volute to reenter the portion of the'vane channels wardly of the vane tip '16" to" induce or acceleratetrifugal component'of the forward fluid flow p the desired helical motion for producing the'advantageous results inthe presentconstruction. k

'Thestr'ength of'the centrifugal componentfof theiitiid .ih vane tips available. 'Acco'rdingly,- FIGURE 2 shows the use of additional splitter vanes'as at 20 which a're placed in impllefadjacent th Pe iph y. the back shroud 12, thesesplitter vanes ZOhavingfthe same regenerative-type tips as' the main vanes 15 'abo've "described.

Operation In operation, when the shaft is rotated bylthe 'prime mover, not shown, the impeller rotates therewith.

' Fluid enters the suction inlet 2 and passes subject to the curvilinear'elfect of the inner face 12 of the annular ring 11 as" above described into the suction eye9' of the impeller wherein a helical motion is imparted thereto" by the tongue-means and thence into the volute 4 in a m-an ner substantially well known'in the art.

However, by reason iofthe regenerative type tips Jas shown' at 17 and the'configuration of'the volute'as"at"18,

-the centrifugal component in the forward motion of the fluid turns aportion of the fluid into those portions'l'of the vane'chaniiels adjacent the periphery of'the back shroud, whereit receives additional momentum-inmoactionwith the vanes of the impeller. This handout movementbetweenthe volute and the vane chan'nelsimparts the added helical motion and causes the'forward motion of the fluid being-pumped to'take on ,anwamplifi ed spiral effect which moves the, gases and lighter-sub- 7 close as :possible to the outerperiphery of the impeller. This tongue is also" extended a slight distance into thevolute as is shown in'FIGURE 2 of the drawings.

Where self-priming characteristics are desired? the tongue will be slotted-as at 2 2 adjacent the wall-ofthe volute. Since the gases andv lighter components 1 are trappedby reason of the hydrodynamic back-flow cutoff elfect of the helical flow pattern, it is believed-that only' the'o'uter heavier layersof liquid returnythro'ugh this slot torassist in continuing the pumpingactioniof the 'pumpfltherebyimparting thedesired self-primingfchar- 'acteristics to thefipump; 2:

Modified form of the invention FIGURE 4 shows a modified form of the invention.

It differs from the form of the invention shown in FIGURE 1 in that the center line of the discharge end of the vane channels are offset from the centerline of the volute. This is done to increase the effective strength of the helical motion induced into the normal fluid flow pattern through the volute.

Thus, except for the volute configuration, all the parts are the same as those described for the form of the invention shown in FIGURE 1 of the drawings and, accordingly, these parts have been given the same character numerals as the parts shown in FIGURE 1.

The volute now designated 4' is shown in crosssection as beginning at the periphery of the back shroud 12 and extending in a somewhat ovoid configuration to a point in the impeller chamber 6 inwardly of the periphcry of the front shroud 14.

This permits a deeper cutout as at 25 to be established on the forward face of the volute 4 and moves the centerline of the volute of the centerline of the discharge end of the vanes 15 as indicated by the lines C and C in FIG- URE 4.

Operation of this form of the invention is the same as that above described for the form of the invention shown in FIGURE 1. However, due to the offset relationship of the centerlines of the discharge end of the vanes 15 and the volute, the inward and outward movement of the fluid flowing through the volute is accentuated, thus increasing the strength of the helical motion imparted to the forward motion of this fluid.

Another form of the invention FIGURE shows a further form of the invention in which an open type impeller 30 has its vanes 31 cut back as at 32 to provide the regenerative tips similar to those above described for the form of the invention shown in FIGURE 1.

The volute 33, however, in this form of the invention is somewhat modified as indicated in FIGURE 5 which shows that in cross section the volute extends from a point in the impeller chamber designated 34 just inwardly of the periphery of the back plate 35 of the impeller in a rectangular-shaped arc to a point where the cutouts 32 of the vanes 31 of the impeller begin.

This permits a portion of the helically moving fluid to pass behind the back plate 35 and return through a plurality of openings 36 to the passages formed between the vanes 31.

Another form of the invention FIGURE 6 shows a still further form of the invention and includes an open impeller 40 having vanes 41 cut back as at 42 to provide the regenerative tip similar to the form of the invention shown in FIGURE 5.

The volute 43 in this form of the invention combines features shown in both FIGURE 4 and FIGURE 5 in that the centerline of the volute as at D" is offset from the centerline D of the discharge end of the vane passages, and further that the volute also extends into the impeller chamber behind and just inwardly of the periphery of the back plate 44 for the impeller.

The cutout portion 45 in the forward face of the volute in this form of the invention is larger for the same purpose as set forth for the form of the invention shown in FIGURE 4 of the drawings.

Both forms of the invention shown in FIGURES S and 6 do not have the curvilinear entrance pattern shown in the FIGURE 1 and FIGURE 4 forms of the invention. However, by reason of the cutout portions forming the regenerative tips on the vanes the desired helical motion is imparted to the forward motion of the fluid passing through the volute.

While the preferred form of pump embodles most all of the features enumerated above it is not intended to so limit the invention as satisfactory swirl of the fluid may be obtained by cutting the volute out as at 59 in a pump having a standard impeller, e.g., one without the cutback means to accomplish the desired helical motion to the forward motion of the fluid passing through the volute.

Of course the helical motion results by providing a V0- lute will cause portions of the fluid being pumped through the impeller into the volute to reenter the impeller.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a centrifugal pump of the self-priming type comprising a volute casing including a discharge outlet, an impeller chamber in said volute casing and communicating with the discharge outlet, a center suction inlet of a predetermined dimension formed in the volute casing and communicating with the impeller chamber, a rotatable shaft mounted in the volute casing and disposed in the impeller chamber, an impeller including a front and back shroud and said back shroud of greater dimension than said front shroud connected to said rotatable shaft and disposed in the impeller chamber, said impeller including vanes forming passage means therebetween and said vanes cut back from said front shroud to a portion thereof having about the same dimension as the back shroud to define a plurality of regenerative tips, the front shroud of said impeller defining an eye of lesser dimension than the dimension of the suction inlet, a suction tube means disposed in'said suction inlet having an outer diameter of substantially the dimension of the suction inlet and said suction tube having an inner surface converging in dimension to form an inner diameter of the dimension of the eye of said impeller to provide a curvilinear flow path to the fluid entering the suction inlet, tongue means comprising extension on each vane and extending into the passage means to reduce the inner dimension thereof whereby a helical motion is imparted to the fluid passing through said impeller, and said regenerative tips coact with the volute casing to impart a helical motion to the forward motion of the fluid passing through said volute to the discharge outlet.

2. The pump claimed in claim 1 wherein the portion of said volute casing adjacent said regenerative tips is cut back to coact with said regenerative tips to amplify the helical motion imparted to the fluid.

3. The pump claimed in claim 2 wherein spiltter vanes are disposed between each adjacent pair of vanes and said splitter vanes include regenerative means formed at the discharge end thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,291,037 Lole Jan. 14, 1919 2,272,469 Lannert Feb. 10, 1942 2,406,499 Jandasek Aug. 27, 1946 2,471,174 Trumpler May 24, 1949 2,736,266 Eisele Feb. 28, 1956 2,737,898 Andermath et a1 Mar. 13, 1956 FOREIGN PATENTS 14,668 Great Britain of 1912 68,264 Netherlands July 16, 1951 80,164 Netherlands Jan. 16, 1956 158,673 Australia Sept. 8, 1954 280,749 Great Britain Nov. 24, 1927 444,333 Germany May 19, 1927 464,510 Germany Aug. 20, 1928 491,977 Great Britain Sept. 13, 1938 912,781 Germany June 3, 1954 

